Probing τ lepton dipole moments at FCC-ee
Abstract
We study the sensitivity of future high-luminosity e+e- colliders to the electromagnetic and weak dipole moments of the τ lepton within the Standard Model Effective Field Theory. We analyse several complementary processes across the FCC-ee operating stages and show that the exceptional luminosity and clean environment of future e+e- colliders allow for substantial improvements over current limits from LEP and the LHC. The e+e- → τ+τ- process provides excellent sensitivity to weak dipole operators through resonant Z production and Z-pole energy scans, while γγ→ τ+τ- yields the strongest constraint on the anomalous magnetic moment owing to the dominance of linear interference effects in the near-threshold region. Higher-energy stages improve the sensitivity to the τ electric dipole moment. The radiative processes e+e- → τ+τ-γ and H→τ+τ-γ provide complementary, though subleading, probes of τ dipole operators. Combining all channels, we estimate the statistical reach at the 95% CL to be |Δaτ|<2.8×10−5, |dτ|<2.5×10−18 e cm, |ΔaτZ|<1.0×10−5, and |dτZ|<4.4×10−19 e cm, improving upon the current bounds by several orders of magnitude. These projections quantify the potential statistical reach of the FCC-ee program, motivating dedicated studies incorporating detector effects, systematic uncertainties, and higher-order theoretical predictions.
Related
- Probing the τ anomalous magnetic and electric dipole moments in photon-induced γγ→τ+τ- production at the FCC-hh
- Dihadron azimuthal asymmetry and light-quark dipole moments at the Electron-Ion Collider
- Electric Dipole Moments as Precision Probes of CP-Violating Top-Quark Interactions in SMEFT
- Electric Dipole Moments in the CP-violating Generational Three-Higgs-Doublet Model
- Bottom quark electroweak dipole moments at a high-energy μ−collider
BibTeX
@misc{buttazzo2026probing,
title = {{Probing $τ$ lepton dipole moments at FCC-ee}},
author = {Dario Buttazzo and Gabriele Levati and Yang Ma and Fabio Maltoni and Paride Paradisi and ZeQiang Wang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.12623},
eprint = {2610.12623},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.12623},
}
RIS
TY - UNPB
TI - Probing τ lepton dipole moments at FCC-ee
AU - Dario Buttazzo
AU - Gabriele Levati
AU - Yang Ma
AU - Fabio Maltoni
AU - Paride Paradisi
AU - ZeQiang Wang
PY - 2026
DA - 2026/10/08
PB - arXiv
DO - 10.48550/arxiv.2610.12623
UR - https://arxiv.org/abs/2610.12623
AB - We study the sensitivity of future high-luminosity e^+e^- colliders to the electromagnetic and weak dipole moments of the τ lepton within the Standard Model Effective Field Theory. We analyse several complementary processes across the FCC-ee operating stages and show that the exceptional luminosity and clean environment of future e^+e^- colliders allow for substantial improvements over current limits from LEP and the LHC. The e^+e^- → τ^+τ^- process provides excellent sensitivity to weak dipole operators through resonant Z production and Z-pole energy scans, while γγ→ τ^+τ^- yields the strongest constraint on the anomalous magnetic moment owing to the dominance of linear interference effects in the near-threshold region. Higher-energy stages improve the sensitivity to the τ electric dipole moment. The radiative processes e^+e^- → τ^+τ^-γ and H→τ^+τ^-γ provide complementary, though subleading, probes of τ dipole operators. Combining all channels, we estimate the statistical reach at the 95% CL to be |Δa_τ|<2.8×10^−5, |d_τ|<2.5×10^−18 e cm, |Δa_τ^Z|<1.0×10^−5, and |d_τ^Z|<4.4×10^−19 e cm, improving upon the current bounds by several orders of magnitude. These projections quantify the potential statistical reach of the FCC-ee program, motivating dedicated studies incorporating detector effects, systematic uncertainties, and higher-order theoretical predictions.
ER -